Size and shape-dependent melting mechanism of Pd nanoparticles

Abstract

Molecular dynamics simulation is employed to understand the thermodynamic behavior of cuboctahedron (cub) and icosahedron (ico) nanoparticles with 2 − 20 number of full shells. The original embedded atom method (EAM) was compared to the more recent highly optimized version as interatomic potential. The thermal stability of clusters were probed using potential energy and specific heat capacity as well as structure analysis by radial distribution function (G(r)) and common neighbor analysis (CNA), simultaneously, to make a comprehensive picture of the solid state and melting transitions. The result shows ico is the only stable shape of small clusters (Pd 55 -Pd 309 using original EAM and Pd 55 using optimized version) those are melting uniformly due to their small diameter. An exception is cub Pd 309 modeled via optimized EAM that transforms to ico at elevated temperatures. A similar cub to ico transition was predicted by original EAM for Pd 923 -Pd 2075 clusters while for the larger clusters both cub and ico are stable up to the melting point. As detected by G(r) and CNA, moderate and large cub clusters were showing surface melting by nucleation of the liquid phase at (100) planes and growth of liquid phase at the surface before inward growth. While diagonal (one corner to another) melting was dominating over ico clusters owing to their partitioned

A universal signature in the melting of metallic nanoparticles

“…Several theoretical [16][17][18] , numerical [19][20][21][22][23][24][25][26][27] and experimental investigations [3][4][5][6][28][29][30][31][32][33] have thus succeeded one another to capture the complexity inherent to the phase changes in nanosized systems. To answer Lord Kelvin's question in full detail, we need to find measurable and computable physical quantities which probe when a solid-liquid (and viceversa) phase change takes place.…”

On the role of ion potential energy in low energy HiPIMS deposition: An atomistic simulation

“…We considered the common neighbor analysis (CNA) method [60,61,62] to characterize the local structure. CNA allows us to distinguish between face centered cubic (fcc) and hexagonal close-packed (hcp) structures which is of practical importance in defect analysis [63,64]. This is achieved by de-termining the angles between the nearest neighbors, and thus the fcc and hcp lattices, having central and mirror symmetry in (111) planes, respectively, can be distinguished by a slight angle difference.…”

Enhanced photoemission from surface modulated GaAs:Ge

“…Nanoparticle model is widely used to study phase transitions at atomistic resolution. [34,35] We would like to remark that the nanoparticle model still enables to understand whether it is As 2 sublimation or pure Ga segregation that motivates Ga nucleation. A detailed description concerning the MD simulation, along with relevant figure (Figure S3) and a movie (Movie S1) is included in the supplementary information.…”